The Role of DNA and Actin Polymers on the Polymer Structure and Rheology of Cystic Fibrosis Sputum and Depolymerization by Gelsolin or Thymosin Beta 4

摘要

Mucus clearance is the first line of pulmonary defense against inhaled irritants, microorganisms, and allergens. In health, the gel-forming mucins are the principal polymeric components of airway mucus but in cystic fibrosis (CF), the necrotic death of inflammatory and epithelial cells releases a network of copolymerized extracellular DNA and filamentous (F-) actin-producing secretions that are similar to pus and difficult to clear by cilia or airflow. The large amounts of F-actin in CF sputum suggested that thymosin β4 (Tβ4) or gelsolin could depoly-merize the secondary polymer network of CF sputum. Dose-dependent CF sputum rheology and polymer structure were measured before and after the addition of excipient, dornase aIfa, Tβ4, gelsolin, and Tβ4 or gelsolin with dornase for 30 min. Sputum was also incubated with Tβ4 30 μg/mL, gelsolin 10 μg/mL or excipient for 0, 5, 10,15, 20, or 60 min. There was a dose-dependent decrease in cohesivity with Tβ4 and a time-dependent decrease in cohesivity at 30 (xg/mL. With the combination of dornase alfa and Tβ4 at 1.5 μg/mL, there was a 65% decrease in elasticity (P = 0.013). There was a time-dependent decrease in cohesivity (P = 0.0004) and elasticity (P = 0.047) with gelsolin and a dose-dependent fall in cohesivity (P = 0.0008). An apparent synergy of Tβ4 or gelsolin on actin and dornase on DNA may be explained by the combined effect of actin depolymerization and DNA filament severing or by virtue of actin depolymerization increasing the effectiveness of dornase alfa.